Gandalf is the wizard who guides the quest in J.R.R. Tolkien’s The Hobbit.
Gandalf visits Bilbo Baggins in Hobbiton and helps organize the expedition to the Lonely Mountain. He brings the dwarves together and encourages Bilbo to leave his sheltered life, although he does not remain with the company for every stage of the journey.
In The Lord of the Rings, Gandalf becomes central to the struggle against Sauron. He is first known as Gandalf the Grey, but after confronting the Balrog on the Bridge of Khazad-dûm, he returns as Gandalf the White. His changed title reflects increased authority and a renewed role in the defense of Middle-earth.
Gandalf belongs to the order of the Istari, spirits sent to Middle-earth to oppose Sauron. Saruman is another member of that order, while Radagast is a separate wizard. Their shared status does not mean they have the same loyalties or responsibilities.